How solar can make data centers more efficient

Pairing solar with data centers may not be a novel idea, but you’ll have a hard time finding companies that rely solely on solar electricity to power their servers. That’s because many of those servers need a reliable power source like the brain needs a steady supply of blood, and solar energy is variable (it flows only when the sun shines).

But what if the use of solar power could help data center owners save energy, reduce the cost of cooling data center equipment and guarantee a steady power supply? That’s the idea that IBM is exploring as it anticipates a greater use of servers that run on direct current (DC) and responds to queries from customers in developing countries where the grid isn’t dependable, said Roger Schmidt, an IBM fellow and its chief engineer for data center energy efficiency.

Using its research lab in Bangalore, India, as a test site, IBM is developing equipment that will make it feasible to use solar power to help eliminate power conversion steps that lead to power losses, which become heat and require the use of cooling equipment. Giant data farm operators such as Yahoo, Facebook and Google are always looking for lower-cost and efficient ways to cool their data centers.

Using solar to directly power data centers is rare, Schmidt said (he said he doesn’t know of any data centers currently doing that). That’s partly because solar production can fluctuate, and a data center needs a steady, uninterrupted supply of power. Marrying the two will require equipment and wiring to adjust the voltage and make sure power from the grid will flow in when not enough solar energy is produced.

The emergence of DC servers is making solar energy, which flows out of solar panels also in DC, a more attractive source of power supply. In a typical rooftop solar system, the solar panels come with an inverter that converts the DC to alternating current (AC) so that it can join the electric grid. In fact, the power that runs from a power plant to your home is all AC, and along the way the AC power goes through equipment to lower its voltage, because many of the appliances and gadgets we use run on much lower voltages.

More efficient conversions

Power reaches data center buildings today in AC, and then it goes through some AC-to-DC-to-AC conversion steps before reaching the servers. Although the servers take in AC (they are AC servers), it actually converts that internally into DC. Each conversion step leads to a bit of power losses; cumulatively the losses add up to a significant amount of power, and they are dissipated as heat. Many companies are working on reducing that power loss, including startups such as Transphorm, which counts Google as an investor.

Some companies in the data center world — from equipment makers to data center operators — have been advocating the use of DC servers and other equipment as a way to eliminate a conversion step or two, which reduces not only power losses but also the amount of money and equipment needed to keep the data center cool. Server manufacturers, including Dell, Hewlett-Packard and of course IBM, have been rolling out DC servers.

Adding solar complements this effort to create a DC microgrid by eliminating an AC-to-DC conversion step. Solar also can be seen as a more reliable source of power for data centers in places like India, where the grid can go down three to four hours a day, Schmidt said. The Indian government has also set a goal of subsidizing the installations of 20 GW of grid-tied solar power and 2 GW of off-grid solar by 2022.

IBM has built a 50 KW solar array on top of its software lab in Bangalore to run its servers. The plan is to add a DC server, an ultrafast IBM Power 775 (which can take AC power as well) and a “smart box” that will be able to take the DC power from solar panels and tweak the voltage to make it suitable to run the server, Schmidt said. The box also will monitor the power flow and make the switch to accept power from the grid when the solar panels aren’t producing much energy or not at all.

“If the move is toward DC power in a data center, the solar array provides a huge opportunity because it provides DC already,” he said. “We want to take advantage and hook directly up to our DC power server in that data center and eliminate some conversion losses.”

IBM, which sells not just servers and software but also services for operating data centers, wants to sell that box and the engineering know-how of wiring a solar array to power a data center, Schmidt said. He declined to say how long the project will take, except that it should be “less than a couple of years.”